Cheers for the heads up. Sunday morning is probably the best time to do it tbh, least amount of traffic. Will it affect saved drafts at all? I've got a half-finished post on the Rendlesham incident that I'd hate to lose if something goes sideways during the maintenance window.
Also out of curiosity - what's actually being worked on? Not being nosy, just always interested in what goes on behind the scenes with these things. If it's server-side stuff it'd explain a few of the slower load times I've been getting this past week or so, pages taking longer than usual to pull up images especially.
Anyway, good that the team flags these things in advance rather than just going dark without warning. Some sites don't bother.